Small-bowel carcinoid tumors are neuroendocrine neoplasms that present unique imaging challenges. In their early stages, the tumors are small and confined to the bowel wall. Small-bowel series and enteroclysis may be more sensitive for detection than CT or MRI. As the tumor grows, extension outside the involved bowel loop may occur, with infiltration of the mesentery and desmoplastic reaction, which results in a characteristic appearance on small-bowel contrast examinations and cross-sectional imaging. In patients in whom there is a high clinical suspicion of carcinoid tumor but inconclusive barium studies or CT, angiography can be performed and may show the submucosal mass because of its vascularity. Alternatively, in this situation, CT angiography may also be used to localize the mass on the basis of its vascularity and in many cases may obviate conventional angiography.
In addition to contrast studies and CT, nuclear medicine techniques using indium-Ill- or iodine-123-labeled octreotide or iodine-131-la-beled metaiodobenzylguanidine (MD3G) are helpful for diagnosing and locating carcinoid tumors and identifying their metastases.
This article reviews the pathophysiology of small-bowel carcinoid tumors and dis-
cusses a variety of radiologic examinations that can be used for the detection, staging, and follow-up of patients with these tumors. A detailed discussion of the value of MDCT and CT angiography is included.
